Patients with relapsed or refractory HER2-amplified biliary tract cancer have few treatment options after first-line therapy. Shubham Pant, MD, Associate Professor, Gastrointestinal Oncology, M.D. Anderson Cancer Center, Houston, TX, presented the results of a phase 1 clinical trial he and his colleagues conducted. The study examined the safety and antitumor activity of zanidatamab, a bispecific (ie, binding to 2 distinct sites on the HER2 receptor) HER2-targeted antibody. The unique antibody geometry of zanidatamab enables it to activate several mechanisms of action after binding to the HER2 receptor.
This multicenter, open-label basket study involved patients with histologically or cytologically confirmed unresectable biliary tract cancer, including gallbladder cancer and intrahepatic or extrahepatic cholangiocarcinoma. The patients had locally advanced or metastatic disease that progressed after ≥1 treatments with a gemcitabine-based regimen. The patients received zanidatamab 20 mg/kg intravenously every 2 weeks.
Treatment with zanidatamab resulted in tumor reduction in the majority (5 of 8) of the patients, translating to a response rate of 65%. Zanidatamab was well-tolerated, with no treatment-related grade 3 or 4 adverse events.
“It was not just the response which was important, but obviously the duration of response. We did see a good duration of response, with patients making it past 4 months, and some patients making it past 6 months,” Dr Pant said.
The global phase 2 clinical trial of zanidatamab monotherapy in HER2-amplified biliary tract cancers is now enrolling patients.
On November 30, 2020, the FDA granted zanidatamab a breakthrough therapy designation for previously treated patients with HER2-amplified biliary tract cancer.
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